Chet Faliszek: Well it really all started with Turtle Rock Studios, a company that has worked really closely with us, updating Counter Strike on the PC with us. They started on it four years ago, but I’ve been on the project for almost two years now.

XCN: Was this always intended to be a zombie game?

CF: Yes! Early on, Michael Booth, the head of Turtle Rock Studios, wanted to make a game that’s entirely A.I. driven, and that’s what Left 4 Dead is. Not only are the creatures attacking you using A.I., and not only are the Bots helping you with A.I. but the game itself is driven by A.I. Meaning that there’s an A.I. Director that sits atop the whole game and it helps with the pacing. Normally in a game you’d say, “Hey we’re going to have combat here.” And as a player you’re thinking, “Once I get done with this combat there’ll be a break over here.” But in Left 4 Dead you never know where you’re going to have combat or where you can expect the break; the A.I. Director procedurally does it the entire time.

XCN: So this is not a scripted game at all?

CF: Exactly! You never know where combat is going to happen. You never know where the breaks are. The cool thing that happens is that it pans out differently every time you play. It does the cool horror movie thing of ‘all hell broke loose’. And you’re just waiting for that bad moment to come pounding down on your guy, right!

XCN: How do you choreograph the drama and the tension if anything can happen at any time?

CF: Well, what will happen is that you have a lot of experiences. For example you’re about to reach the escape vehicle and all’s going well, there’s two guys left alive… there are two dead, but okay, there are two guys who are going to escape and they’re happy because they’ve been trying this a few times. You’re about to step out on the escape vehicle and a Smoker comes and grabs the guy and takes him away. You couldn’t have scripted it better than that. It creates these great moments that you hear people coming back and talking about with each other.

XCN: How big is the world, and how is it laid out – in chapters, or a continuous open world?

CF: There are four scenarios, each broken down into five maps or ‘Chapters’. Like most movies they’re 1.5 to 2.5hrs long for a new player. It’s an experience that players can have online together over an evening. Let’s say you just want to go out and play for a while, you’re not going to want the full eight-hour experience right? Our wives and loved-ones would not let us! But in an hour and half you can have the feeling that we started something and we ended it.

XCN: Let’s talk about the zombies some more. In the movies, zombies are usually stupid and slow. What kind of A.I. does a slow and stupid zombie have?

CF: The common ‘Horde’ is definitely your class of kind of dumb zombies. They’ll wander around in a stupor and not really do anything until you set them off and they’ll come running after you. They’re not really coming after you. But the infection is also mutated, and the mutations will come in the form of The Smoker who has a 50ft prehensile tongue, we’ve got the Boomers – bug giant guys filled with gas, and if he vomits on you you’re covered in bile and all the infected in the area will come after you. There’s a Hunter, which leaps – and if he pounces on you he’ll rip you apart until someone comes and gets him off. And then the Tank is just this big giant bruising guy who can just punch you and send you sailing!

They’re all cool for their own reasons, but they all fill a need in the co-op sense. If you’re trying to run ahead the Hunter’s going to pounce you and you’ll be dead if your friends aren’t close behind. If you’re really tight as a group, a Smoker will come and pull one guy out. The Boomer will blind some of your guys, so they’ll need your help and protection. The Tank is a big giant guy but he’s really easy to kill if you all stick together, all focus on him and go after him. But if you don’t he’s really hard to kill, so it’s all about teamwork and staying together in co-op.

XCN: In addition to the weapons, are there any cool gadgets that can be used against the zombies?

CF: See, the game is about these four survivors who aren’t military, who aren’t trained. It’s kind of like you or I. They don’t even know each other until this starts, so the weapons they have available to them are what they find in that kind of situation. You’ll see your assault rifle, your shotgun, things that you might find in the hunting store. Equally though there have been Molotovs that some people have put together, and you also have the Pipe Bomb. Some players have already figured out that the Infected get set off by noises; if you throw it the infected go crazy for it. And when they touch it they all blow up.

XCN: How much can players affect the environment? Can I collapse buildings, explode vehicles and use these against the infected?

CF: On the infected side, let’s say if you came out as a Tank you could smash these cars around. You can also bash through some of the walls. Only in the finale do you make a stand, and there you’re given extra tools like propane tanks and petrol cans, sometimes you might have a mounted gun, or other stuff that’ll help you get through the world.

XCN: What have you seen that’s most surprised you in the gameplay?

CF: So much! We have so many testers come through Valve – it’s been a twice a week event during the course of development. We don’t just believe in testing at the very end. We use that in how we design the games. So from the very get go we have testers there.

We really had a good starting point with what Turtle Rock had done, we’ve had a strong vision of the game for a while. One of the things that it does, unlike a game like Counter Strike, it became really clear that this is a game that, when you play with your friends, horrible things happen to you and you just laugh! You have a fun time! And that’s what a zombie apocalypse should be!

I’ve always been a huge zombie and horror fan. This has been a chance to go into that world. I wanted to make sure that we had our own fiction and our own world.

XCN: Where do you stand on the whole slow versus fast zombies issue?

CF: We’re in the fast zombie camp here! They’re gonna come running after you and it’s going to be horrific!